1. Field of the Invention
The present invention relates to a device or apparatus for preventing the oxidation of a tack weld along a weld seam of two pipes. More specifically, the present invention relates to a hand tool that reflects an inert source gas towards the interior surface of a weld site along a weld seam of two pipes in order to prevent the oxidation of the weld site.
2. Discussion of Background
In the formation of high quality pipe welds for both low-alloy and high-alloy steel pipes, for example stainless steel pipes, it is common practice to bring the pipe ends together at the junction at which the weld seam is to be formed and tack-weld the ends of the pipes together. This serves to provide a stable, aligned work piece for the final weld. Additionally, prior to tack welding the weld seam, it is common to bevel the ends of the pipes, so as to provide a suitable weld surface.
Typical applications to perform this tack-weld include gas tungsten-arc welding, also known as tungsten inert gas (TIG) welding. The TIG welding process is used for a wide variety of metals, particularly aluminum, magnesium, titanium, and refractory metals. During the TIG welding process, a filler metal may be used which is usually composed of a material similar to the metals being welded. Additionally, a shielding gas is supplied during this process which usually includes argon, helium, or a mixture of the two. The shielding gas serves to prevent the oxidation of the weld metal as the high temperature nature of welding increases the oxidation rate of the weld metal.
Usually, when performing these tack-welds, it is necessary to provide two shield gases, a source gas and a back gas. The source gas flows from the welder itself and is directed towards the top of the weld site to prevent the top of the tack-weld from oxidizing. The back gas prevents the interior surface of the tack-weld from oxidizing and can be supplied by two different methods. First, the back gas can be supplied by inserting a gas tube down the length of the pipe, or second, by drilling a tap hole through one of the pipes and then inserting the gas tube. In both instances, the ends of the pipes are capped, thus, in effect, flooding the interior of the pipe with the back gas. The source gas and back gas combine to prevent the oxidation of the tack-weld and surrounding metal. The inert gas used in the source gas and back gas is costly, thus significantly increasing the expense of the weld. Therefore, reducing the quantity of or the need of a back gas would significantly reduce the costs of such welds.
It is known to flood the back side of the weld area with an inert, shield gas to prevent the oxidation of the weld, during the complete welding process. In U.S. Pat. No. 5,235,152, Jankus discloses a device that forms an annular ring within the pipe thereby reducing the volume that must be flooded with a back gas. However, there still remains a need for a more efficient method and apparatus for reducing the amount of gas required for the TIG tack-welding process, while still preventing the oxidation of the interior surface of the tack-weld site.